Plug construction for a concrete anchor insert

ABSTRACT

A pair of plastic plugs adapted to be threaded into the opposite ends of the helical coil of a conventional concrete anchor insert in order to prevent seepage of concrete into the coil during a concrete pouring operation around the insert and also to provide for visual location of the anchor insert after the concrete has set. The plug for the exposed or upper end of the coil of the anchor insert embodies an upstanding, flexible, locating prong which, in the free state of the plug, is straddled by a pair of torque-applying wings, the latter being for use in threading the plug into the exposed end of the coil and adapted to break away from the locating prong at such time as the plug is threaded or turned to its home position in the coil thus leaving the prong exposed on the upper surface of the hardened concrete for anchor insert locating purposes.

United States Patent [1 1 Tye [4 1 July 3,1973

[ PLUG CONSTRUCTION FOR A CONCRETE ANCHOR INSERT [75] Inventor: Dennis W. Tye, Fremont, Calif.

[73] Assignee: Superior Concrete Accessories, Inc., Franklin Park, 111.

[22] Filed: Feb. 9, 1972 [21] Appl. No.: 224,901

[52] U.S. Cl. 52/98, 52/705 Primary Examiner-John E. Murtagh Attorney-Norman H. Gerlach [57] ABSTRACT A pair of plastic plugs adapted to be threaded into the opposite ends of the helical coil ofa conventional concrete anchor insert in order to prevent seepage of concrete into the coil during a concrete pouring operation around the insert and also to provide for visual location of the anchor insert after the concrete has set. The plug for the exposed or upper end of the coil of the anchor insert embodies an upstanding, flexible, locating prong which, in the free state of the plug, is straddled by a pair of torque-applying wings, the latter being for use in threading the plug into the exposed end of the coil and adapted to break away from the locating prong at such time as the plug is threaded or turned to its home position in the coil thus leaving the prong exposed on the upper surface of the hardened concrete for anchor insert locating purposes.

5 Claims, 6 Drawing Figures PATENIEU JUL 3 I975 SHEET 1 UF 2 FIG. 2

FIG. 4

PLUG CONSTRUCTION FOR A CONCRETE ANCHOR INSERT The present invention relates to an improved plug construction for use in connection with an anchor insert of the type which comprises an open-ended helical coil, is adapted to be set in place within a concrete slab form or the like prior to a concrete pouring operation for slab-forming purposes and, after the concrete has been poured and become set, establishes a threaded socket for reception of a lag screw therein, the lag screw constituting a fixed reaction anchor by means of which the hardened concrete slab may be detachably connected to a crane or other hoisting mechanism.

Such a concrete anchor insert is well-known and invariably takes the form of a tightly wound helical coil having associated therewith chair-like or other supporting means whereby the insert is held in place during one or more concrete pouring operations. Because the coil is tightly wound, concrete seepage into the coil through adjacent coil convolutions is not possible but some type of means must be provided for plugging the ends of the coil and thus preventing the entrance or intrusion of concrete into the coil through the ends thereof. Early means for accomplishing this consisted in the use of corks or either sponge rubber or plastic foam plugs requiring removal of the upper plug from the coil prior to threading of a lag screw into the coil, and the lower plug being subject to disintegration when the lag screw is threaded into the coil. A plug construction of such character possesses the common disadvantage that it is difficult to locate and expose the associated anchor insert after a given concrete pour has become set or hardened, this being the result of the fact that there is no visible evidence of the position of the insert within the concrete. More recently, it has been suggested that the plug for temporarily plugging or closing the exposed or upper end of the coil which lies adjacent to the upper surface of the poured concrete slab shall be so constructed that it will afford in said upper surface of the concrete a localized discolored area inthe vicinity of the anchor insert. Although this expedient may be of value in many instances, it is not altogether infallible due to the presence of other discolorations which may be present in the concrete surface.

The present invention is designed to overcome the above-noted limitations that are attendant upon the construction and use of present-day plug constructions for the ends of tightly wound open-ended coils of conventional concrete anchor inserts and, toward this end, the invention contemplates the provision of two'plugs, namely, a lower plug of hollow one-piece plastic construction which is proportioned for snug reception in the lower end of the coil of the associated anchor insert and, more importantly, an upper plug which likewise is of hollow one-piece plastic construction and is proportioned for snug reception in the upper end of said coil prior to a concrete pouring operation around the insert. This upper plug is designed for threaded reception in the upper end of the coil and, accordingly, :1 limited section thereof, i.e., less than one complete thread turn or convolution, is made to match the internal threaded bore of the coil so that, by a single short turn of the wrist, the plug may be installed in the upper end of the coil. To facilitate turning of the upper plug during such installation thereof, a flat wing-like structure extends upwardly from the upper end of the plug and constitutes, in effect, a torque-applying key wing which is used by the operator when installing the upper plug in the upper end of the coil of the anchor insert. The key wing is extremely (paper) thin and flexible yet it possesses sufficient rigidity that, as it is turned, the associated upper plug is threaded into the open upper end of the coil as heretofore described. However, when the upper plug is driven to its home position in the coil, the counter-torque or reaction which develops causes the key wing to fracture and break away, leaving only a thin upstanding flexible rod-like locating prong which projects above the uppermost level of the concrete slab undergoing formation. Because such prong is flexible, it offers no resistance to the usual screeding operation wherein a screed board is used to level off the concrete, the prong merely flexing to one side as the screed board passes thereover and thereafter rising to its normal vertical position as soon as the screed board has released the prong. After the concrete slab has become set or hardened, the prong is plainly visible and may thus bev readily located so that the thin crust of concrete which overlies the upper plug may be broken away preparatory to unthreading or other removal of the plug from the coil and the threading in its place of a lag screw for slab hoisting purposes.

The provision of a readily locatable plug such as has briefly been outlined above, and possessing the stated advantages, constitute the principal object of the present invention. Other objects and advantages of the invention, not at this time enumerated, will readily suggest themselves as the nature of the invention is better understood from a consideration of the following detailed description.

The invention consists in the several novel features which are hereinafter set forth and are more particu larly defined by the claims at the conclusion hereof.

In the accompanying two sheets of drawings forming a part of this specification, a preferred and exemplary form of the invention is shown.

In these drawings:

FIG. I is a side elevational view of a conventional concrete anchor insert of the helical coil type, such view illustrating, in exploded fashion, a plug construction embodying the present invention immediately prior to application of the upper and lower plugs thereof to the upper and lower ends of the helical coil of the inserts;

FIG. 2 is a side elevational view similar to FIG. I but showing the two plugs operatively installed in the helical coil of the associated anchor insert;

FIG. 3 is an exploded perspective view of the plug construction, such view illustrating in detail the nature of the frangible torque-applying key wing of the upper P g;

FIG. 4 is a horizontal sectional view taken on line 4-4 of FIG. 3;

FIG. 5 is an enlarged fragmentary sectional view taken centrally and longitudinally through the anchor insert and the two plugs of the plug constructiongthe upper plug being shown without its torque-applying key wing; and

FIG. 6 is a fragmentary perspective view showing an anchor insert having the plug construction of the present invention applied thereto and a concrete slab having similar anchor inserts embedded therein and illustrating schematically their mode of operation.

Referring now to the drawings in detail, and in particular to FIG. 6, there is disclosed in this view a completely assembled anchor insert resting on a foundation surface 12 and alongside a concrete slab 16 which has embedded therein a plurality of similar anchor inserts 10. One of the embedded inserts is shown in its normal condition with a certain torque-applying key wing protruding from the upper surface of the concrete slab preparatory to being wrested therefrom, another insert being shown in the condition which it assumes after the aforementioned key wing is broken away so as to leave a visible locating prong protruding or extending upwards from the concrete slab 16, and yet another insert being shown in an exposed condition for reception therein of a lag screw by means of which the slab 16 may be hoisted for tilt-up purposes, all in a manner that will be made clear subsequently.

The various anchor inserts 10, except for the provision of the particular plugs which are associated therewith, are generally of conventional construction and are of the type which is shown and described in US. Pat. No. 3,216,171, granted on Nov. 9, 1965 and entitled CONCRETE ANCHORING INSERT AND METHOD OF PREVENTING CONCRETE SEEP- AGE THEREIN. Each such insert includes a vertically extending, tightly wound helical coil 20 and a series of four generally L-shaped legs 22. The latter are separately formed from the coil but are welded thereto so that the legs and coil constitute a unitary composite chair-like structure.

The four L-shaped legs 22 are identical in construction and each leg includes a substantially straight vertical part 24 and a generally horizontal part 26. The upper regions of the. vertical parts 24 are welded to spaced apart outer portions of the helical coil 20. The horizontal parts 26 of the legs 22 diverge radially outwardly from'one another and are of irregular configuration, each such horizontal part including a U-shaped bight portion 28, the four bight portions establishing a series of supporting feet for the legs as a whole and by means of which the insert 10 may be supported on the foundation surface 12. The legs 22 are formed of medium gauge wire and serve, in connection with the formation of the wall slab 16, to space the helical coil 20 upwardly from the upper face of the foundation surface 12 and cause the same to assume a vertical position with its upper end disposed slightly below the level at which concrete pouring operation or operations terminate.

With the anchor insert 10 thus positioned on the foundation surface 12, the helical coil 20 defines an internal screw thread which is designed for reception therein of the shank portion 30 of a lag screw 32 by means of which slab-hoisting operations may be resorted to as, for example, in the manner and for the purpose set forth in aforementioned US. Pat. No. 3,216,171.

The arrangement of parts thus far described is purely conventional and no claim is made herein to any novelty in the same, the novelty of the present invention consisting rather in the application to the helical coil 20 of a pair of plugs consisting of an upper plug and a lower plug 42. It will be understood that the upper plug 40 is adapted for limited threaded reception in the upper open end of the helical coil 20 of the anchor insert 10 and when so received therein, precludes the entrance of poured concrete into the coil. Similarly, the

lower plug 42 is adapted for limited threaded reception in the lower open end of the coil 20 for the same purpose.

Considering first the character of the lower plug 42, this plug is in the form of a hollow shell-like body which preferably is formed of a suitable thermoplastic material and is generally of cylindrical configuration and of appreciable axial extent. The extreme upper end of the plug 42 is contoured for threaded reception in the lower end of the helical coil 20 and is formed with an external contour thread 44 for this purpose. The contour thread is relatively short and preferably is no greater than one helix turn so that a correspondingly short amount of turning movement of the lower plug 42 will be required to force it to its home position within the lower end of one coil at the time of installation thereof in said coil. An abrupt lateral shoulder 46 terminates the extent of the contour thread 44 in order to avoid binding of the latter within the coil. Notch-like recesses 47 at diametrically disposed regions of the lower rim of the side wall of the base of the lower plug 42 facilitate threading of the element in position within the coil. A small opening 48 (see FIGS. 3 and 5) is formed centrally in the top wall 49 of the body of the lower plug 42 and serves a function that will be made clear presently.

The upper plug 40 is likewise in the form of a hollow shell-like body but is of extremely small axial extent. It is formed of any suitable thermoplastic material and preferably by an injection molding operation. A short contour thread 50 which is similar to the thread 44 and terminates in an abrupt shoulder 52 allows for limited threaded reception of the upper plug 40 into the upper end of the helical coil 20. Diametrically opposite notch-like recesses 54 in the upper side portions of the body of the upper plug 40 facilitate removal of said plug from the surface of the concrete slab 12 at such time it is required that the upper plug be thus removed.

As best shown in FIGS. 1 and 3, the top wall 56 of the upper plug 40 is formed with an upstanding, substantially planar, generally trapezoidal wing-like structure 58 which, in effect, constitutes a torque-applying key wing by means of which a limited amount of torque may be applied to the upper plug 40 for the purpose of causing it to become initially threaded into the upper open end of the helical coil 20 of the annular insert 10.

This wing-like structure which hereafter will be referred to as the key wing 58 embodies a frangible outer portion 60 (see particularly FIG. 2) which is of inverted U-shape configuration, is normally centered, so to speak, about a disposed, upstanding flexible locating prong 62, and is connected to said prong and also to said top wall 56 by means of a paper-thin membrane 64 (see FIGS. 1 and 3) due to the upper plug being formed by an injection molding operation. In the free molded condition of the upper plug 40 as it emerges from the mold, the key wing 58 and its associated locating prong 62 are reasonably rigid so that the key wing may be used as the torque-applying member or tool for threading the upper plug into the upper end of the coil 20. However, when this is done and the shoulder 50 of the contour thread 52 engages the adjacent end of the coil, rotation of the upper plug 40 abruptly terminates and the continued manual effort which is applied to the turning of the plug 40 causes the frangible outer portion 60 to become wrested loose from the central locating prong 62 as schematically illustrated in FIG. 2,

thereby leaving said prong centrally disposed on the top wall 56 of the upper plug 40. With the prong 62 thus released from the confining key wing, the prong is free to flex in all directions as indicated in dotted lines in FIG. 5 of the drawings.

In using the anchor insert and its associated upper and lower plugs 40 and 42, the insert is first prepared by assembling the upper and lower plugs thereon so that the parts assume the condition in which they are shown in FIGS. 5 and 6. This is accomplished by threading the two plugs into the opposite open ends of the coil in the manner previously described, care being taken in applying the upper plug 40 to the coil that the rupture factor of the frangible torque-applying key wing 58 be not exceeded during this initial assembly of the anchor insert as a whole. As soon as the insert is thus prepared, it is placed at the desired location on the foundation surface 12 and within the concrete slab form (not shown) so that the top wall 49 of the upper plug 40 is disposed at or slightly below the ultimate finish level of the concrete which is to be poured into the aforementioned form. With the assembled anchor insert so placed, the wet concrete is poured to the desired level.

If, as almost invariably is the case, slab surface finishing operations are to be conducted prior to allowing the poured concrete to become set, wresting of the frangible outer portion 60 of the key wing 58 from the upper plug 40 will be performed so that the upstanding locating rod 62 will be released and will project centrally and upwardly from the plug 40. It is to be understood that snap off of the key wing 58 may take place either at the plant where the anchor insert is assembled or at the site where the insert is to be used. When the aforesaid locating-prong encounters the usual screed board in passing, the prong 62 will become deflected laterally as shown in dotted lines in FIG. 5. As soon as this locating prong 62 is released by the screed board, the same will return to its normal vertical position because of the inherent memory characteristics of the plastic material of which the plug 40 is formed.

The particular time at which wresting of the frangible portion 60 of the torque-applying key wing 58 from the upper plugging member 40 is resorted to may, as heretofore indicated, be varied in accordance with the particular nature of the involved slab installation. If the anchor insert 10 is positioned in the vicinity of a corner or an edge of the slab where the key wing 58 is readily accessible with the insert 10 in situ within the poured concrete of the slab, wresting of the frangible portion 60 may take place after the concrete is poured, the relatively great mass of wet concrete serving as the reaction force to prevent bodily turning of the insert 10 when fracturing torque is applied to the key wing 58. On the other hand, if the insert 10 is to be located in the central region of the slab where the key wing ordinarily would be inaccessible, wresting of this frangible portion 60 may be accomplished at the time of the initial assembly of the insert and placement thereof into the concrete slab form.

It is to be noted at this point that the disclosure of FIG. 6 is not a true representative view of a concrete slab installation embodying a number of the inserts 10. It is merely a schematic view which illustrates certain principles which are involved in the use of the inserts 10. In connection with one of the three inserts 10 shown in this view, the frangible outer portion 60 of the key wing 58 is shown in broken lines to illustrate that this frangible portion was wrested from its position prior to hardening of the concrete of the slab. No situation is likely to arise where this frangible portion 60 remains on the upper plug 40 until after the concrete has hardened. The anchor insert 10 with which the upwardly extending locating prong 62 is associated is representative of the fact that because such insert is disposed in the medial region of the slab where it is not within reach of the operator, the frangible portion 60 was wrested from the plug 40 prior to positioning of the insert within the slab form.

Considering now that the concrete of the slab has become set, and that it is desired to locate one of the inserts 10 for the purpose of lag screw application thereto, it is necessary merely to loosen the thin layer of concrete which may exist immediately above the insert and then, when the upper face of the upper plug 40 has become bared, insert a suitable torque tool such as a spanner wrench or the like into the notches 54 and unscrew the upper plug from the upper end of the coil 20. Such unthreading of the upper plug from the coil 20 is greatly facilitated by the provision of the abrupt abutment or shoulder 52 at the end of the wire coil 20 which prevents binding of the plug 40 within the coil at the time it initially reaches its home position. The upper plug 40 may also be removed by wedging it out of its operative position by way of a screw driver or the like. Thereafter a lag screw such as the illustrated lag screw 32 may be threaded deep into the coil through the upper open end thereof and used as a reaction point for subsequent slab hoisting operations in the manner set forth in aforementioned US. Pat. No. 3,216,171.

The present invention is largely concerned with the nature of the upper plug 40, the character of the lower plug 42 being of less significance. However, it is to be noted that the aforementioned hole or opening 48 which is formed in the top wall 49 of the lower plug may allow the lower tapered end of the lag screw to penetrate the interior of the hollow lower plug 42, after which the powerful downward thrust of the lag screw will cause the hole 48 to become widened so that the lag screw may progressively enter the confines of the hollow lower plug. In the event that the lag screw is not sufficiently pointed, or if a lag bolt is used, then the downward thrust of the lag screw may collapse the top wall 49 and at least partially dislodge the plug 42 from the coil 20. Since this lower plug remains within the confines of the concrete slab 16, what becomes of it is of no significance.

The invention is not to be limited to the exact arrangement of parts shown in the accompanying drawings or described in this specification as various changes in the details of construction may be resorted to without departing from the spirit or scope of the invention. Therefore, only insofar as the invention is particularly pointed out in the accompanying claims is the same to be limited.

Having thus described the invention what I claim as new and desire to secure by Letters Patent is:

1. In a plug construction of the character described, a molded plastic plug for use in sealingly closing the normally open upper end of a tightly wound helical coil associated with an anchor insert to prevent entrance of concrete into the coil during concrete slab pouring operations, said plug comprising a generally cylindrical body having its lower end provided with an external contour thread by means of which the plug is caused to enter the coil in tight fitting relationship by a threading operation, a flexible locating prong integrally formed on said upper end surface of the plug, normally projecting axially upwardly from such surface, and adapted for momentary deflection under the influence of its contact with a screed board during concrete levelling operations, and a frangible torque-applying member formed integrally on said plug, surrounding the prong, and projecting generally radially outwardly from said plug, said torque-applying member being adapted for wresting from said prong when the plug reaches its home position within the coil in connection with turning of the plug into connected relation with the upper end of the coil.

2. A molded plastic plug as set forth in claim 1 and wherein said torque-applying member is in the form of a flat key wing which extends in diametric fashion across said upper end surface of the plug and lies in the general plane of said prong.

3. A molded plastic plug as set forth in claim 2 and wherein said torque-applying member is connected to the prong, and also to said upper end surface of the plug, by a frangible paper-thin membrane which becomes ruptured when a predetermined torque-applying factor is exceeded.

4. A molded plastic plug as set forth in claim 3 and wherein said generally cylindrical body is of hollow shell-like construction.

5. In a plug construction of the character described, a one-piece, molded plastic plug for use in sealingly closing the normally open lower end of a tightly wound helical coil associated with an anchor insert to prevent entrance of concrete into the coil during concrete pouring operations, said plug comprising a generally cylindrical hollow body having its upper end provided with an external contour thread by means of which the plug is caused to enter the coil in tight fitting relationship by a threading operation, said body having a cylindrical side wall and generally circular top and bottom walls, said side and bottom wall of the hollow body being formed with a pair of diametrically disposed notch-like recesses therein to facilitate the application of torque to the plug during threading of the latter into said coil, said top wall of the body having formed in the central portion thereofa small diameter opening for reception of the pointed end of a lag screw when the latter is threadedly received in said coil from above. 

1. In a plug construction of the character described, a molded plastic plug for use in sealingly closing the normally open upper end of a tightly wound helical coil associated with an anchor insert to prevent entrance of concrete into the coil during concrete slab pouring operations, said plug comprising a generally cylindrical body having its lower end provided with an external contour thread by means of which the plug is caused to enter the coil in tight fitting relationship by a threading operation, a flexible locating prong integrally formed on said upper end surface of the plug, normally projecting axially upwardly from such surface, and adapted for momentary deflection under the influence of its contact with a screed board during concrete levelling operations, and a frangible torque-applying member formed integrally on said plug, surrounding the prong, and projecting generally radially outwardly from said plug, said torque-applying member being adapted for wresting from said prong when the plug reaches its home position within the coil in connection with turning of the plug into connected relation with the upper end of the coil.
 2. A molded plastic plug as set forth in claim 1 and wherein said torque-applying member is in the form of a flat key wing which extends in diametric fashion across said upper end surface of the plug and lies in the general plane of said prong.
 3. A molded plastic plug as set forth in claim 2 and wherein said torque-applying member is connected to the prong, and also to said upper end surface of the plug, by a frangible paper-thin membrane which becomes ruptured when a predetermined torque-applying factor is exceeded.
 4. A molded plastic plug as set forth in claim 3 and wherein said generally cylindrical body is of hollow shell-like construction.
 5. In a plug construction of the character described, a one-piece, molded plastic plug for use in sealingly closing the normally open lower end of a tightly wound helical coil associated with an anchoR insert to prevent entrance of concrete into the coil during concrete pouring operations, said plug comprising a generally cylindrical hollow body having its upper end provided with an external contour thread by means of which the plug is caused to enter the coil in tight fitting relationship by a threading operation, said body having a cylindrical side wall and generally circular top and bottom walls, said side and bottom wall of the hollow body being formed with a pair of diametrically disposed notch-like recesses therein to facilitate the application of torque to the plug during threading of the latter into said coil, said top wall of the body having formed in the central portion thereof a small diameter opening for reception of the pointed end of a lag screw when the latter is threadedly received in said coil from above. 